Ferromagnetic material



United States Patent Ofitice 3,085,980 Patented Apr. 16,, 1963 Thisinvention relates to ferromagnetic materials which have valuableelectromagnetic properties.

The ferromagnetic material according to the invention has a crystalstructure similar to that of the mineral garnet and is characterized bya composition according to the formula As compared with :knownmaterials, the materials according to the invention have improvedproperties in several respects. initial permeability, a lower value ofthe saturation magnetisation, which when used in microwave equipment isimportant for comparatively long wave-lengths and a lower value of thelosses.

Materials in which in the said formula have a higher value for theinitial permeability, while the electromagnetic losses are very low.

Materials, in which in the said formula have very low values for theelectromagnetic losses. The same is true of the materials in which inthe said formula Materials, in which in the said formula have lowervalues for the magnetic saturation than the material Y 'Fe Fe O The sameis true of the materials in' which in the said formula and of materialsin which in the said formula The materials according to the inventionare preferably manufactured by sintering a finely-divided mixture,chosen approximately in the correct ratio, of the compocarbonates,oxalates and acetates. These properties are a hlgher value of the nentmetal oxides of the new compounds. It is naturally possible to replacethe metal oxides by compounds converting into metal oxides upon heating,for example, The term correct ratio is to be understood herein to mean aratio of the amounts of metals in the initial mixture equal to that inthe materials to be manufactured. If desired, the finely-divided initialmixture may first be presintered, the reaction product again pulverizedand the resultant powder again sintered, which series of operations maybe repeated, if desired, once or several times. The sintering processfor the final sintering process takes place between 1200 and 1500 C.preferably between 1350 and 1450 C., for about one to ten hours in agaseous atmosphere having a content of oxygen higher than air. With thematerials having a high-content of calcium and silicon the sinteringprocess preferably takes place between 1200 C. and 1300 C.

Bodies consisting of the novel ferromagnetic materials 7 may be obtainedeither by sintering the initial mixture of after the addition of abinder, into the desired form and subjecting it to afinal sinteringprocess;

Example 1 Mixtures of yttrium oxide, calcium carbonate, titanium oxide,magnesium carbonate, silicon oxide and ferric oxide were ground in thedry state in a porcelain mortar for 15 minutes. The mixtures werepre-sintered in oxygen at 1400 C. for 2 hours. The reaction productswere subsequently pulverized with the use of ethyl' alcohol'in an agatemortar for 5 minutes and then ground in a shaking mill with the use ofethyl alcohol for 4 hours. After drying and addition of some drops ofwater, the powders were moulded to form rings, which were heated at 1400C. in an atmosphere containing principally oxygen for 4' l kc./s. 30kc./s. 400 kc./s. 3 Mc./s. 41rM ,u' tanfi n tan 5 tan 5 p tan 5YaFcgFegou 1, 700 90 5 0. 02 80 0. 07 60 0. Y: 75030.25F01 5Tl0 Fea01160 150 0. 18 Ya 502105150 5Tiu 5FG3O g 320 270 O. 11 Ya 4C30,uF04Tl0.uF0nO 2 420 0. O4 320 0. 14 220 O. 13 Ymoao Fe ,aTio FGzOrg. 370 O.04 320 0.12 300 O. 05 YzCttFeTlFeaOn 220 Y2 KECHOMFQi .tTlo uFCaOiI- 325O. 04 300 0. O5 270 0. ()4 Y2 25080.7:F81 .aTlo 7Feaorz 340 O. 05 310 0.05

What is claimed is: 1. A ferromagnetic material having a crystalstructure similar to that of the mineral garnet and a composition 20according to the formula 3Bb aCeLFe; wherein a is not greater than 2.7 bis not greater than 0.3 m is not greater than 1.2 n is not greater than1.5 x is not greater than 2.7 y is not greater than 0.5 a+b+m+n+x+y isnot less than 0.009 a+b is not greater than 2.7 and x+y is not greaterthan 2.7

2. A ferromagnetic material as defined in claim 1, in which a is greaterthan zero and not greater than 1.2 b=0 m is greater than zero and notgreater than 1.2 n equals zero x equals zero y equals zero a equals m 3.A ferromagnetic material as defined in claim 1, in which a is greaterthan zero and not greater than 2.7 b=0 m is greater than zero but notgreater than 1.2 n=0 a is greater than m 4. A ferromagnetic material asdefined in claim 1, in which a is greater than zero but not greater than2.7

x is less than 2.7 y=0 a is greater than x 6. A ferromagnetic materialas defined in claim 1, in

which a equals zero b is not greater than 0.3 m equals zero 21 equalszero x is less than 0.5

y is not greater than 0.5 y is greater than b-I-x 7. A ferromagneticmaterial as defined in claim 1, in

which a is greater than 0 and not greater than 2.7 b equals zero mequals zero It equals zero x is greater than 0 and not greater than 2.7y equals zero a equals 2:

8. A ferromagnetic material as defined in claim 1, in

which a equals zero b is greater than zero and not greater than 0.3 mequals zero n equals Zero x equals zero y is greater than zero and notgreater than 0.3 b equals y 9. A ferromagnetic material as defined inclaim 1, in

which a equals zero b equals zero m equals zero n equals zero x isgreater than zero and less than 0.5 y is greater than zero and less than0.5 x=y 10. A ferromagnetic body consisting essentially of ahighly-coherent sintered mass of crystals having a crystal structuresimilar to the mineral garnet, said crystals having a compositioncorresponding to the formula wherein a is not greater than 2.7

b is not greater than 0.3

m is not greater than 1.2

n is not greater than 1.5

x is not greater than 2.7

y is not greater than 0.5 a+b+m+n+x+y is not less than 0.009 a+b is notgreater than 2.7

x+y is not greater than 2.7

11. A method of manufacturing a ferromagnetic material having a crystalstructure similar to the mineral garnet comprising the steps, forming amixture of yttrium oxide, calicum oxide, cerium oxide, iron oxide,titanium oxide, magnesium oxide, silicon oxide and beryllium oxide inproportions corresponding to a composition having the formula a is notgreater than 2.7

b is not greater than 0.3

m is not greater than 1.2

n is not greater than 1.5

x is not greater than 2.7

y is not greater than 0.5

a+b+m+n+x+y is not less than 0.009

a+b is not greater than 2.7

and

x+y is not greater than 2.7

25 12. A method as defined in claim 11 in which the 6 temperature atwhich the mixture is heated is between 1350 C. and 1450 C.

13. A method as defined in claim 11 in which the mixture after heatingis pulverized and reheated to said temperature.

14. A method as defined in claim 11 in which for a mixture with a highcontent of calcium and silicon, the heating temperature is about 1200 C.to 1300 C.

15. A method as defined in claim 11 in which the mixture is compactedinto a body and heated.

Bertaut et a1.: Comptes Rendus, vol. 242, pp. 382-384 (1956).

Aleonard et 31.: Comptes Rendus, vol. 242, pp. 2531- 2533 (1956).

Pauthenet: Comptes Rendus, vol. 243, pp. 1499-4502 (1956).

Maxwell et a1.: Physical Review, Dec. 15, 1954, pp. 1503, 1504.

Epstein et al.: I. of Applied Physics, April 1959, p. 2958.

1. A FERROMAGNETIC MATERIAL HAVING A CRYSTAL STRUCTURE SIMILAR TO THATOF THE MINERAL GARNET AND A COMPOSITION ACCORDING TO THE FORMULA